Multi-layered insulated containers made from folded blanks are disclosed in the following U.S. Pat. Nos. 5,660,326, 5,697,550, 5,964,400 6,085,970, 6,196,454, 6,257,485, 6,378,766 and 6,422,456, which disclosures are incorporated herein in their entireties by this reference. Although the inner and outer portions of the container (that is, the sidewall) are prepared from a single blank, when assembled, the sidewalls of such containers effectively comprise three layers due to an insulating liner being sandwiched between the folded inner and outer layers. One version of the insulating container disclosed in the referenced patents is sold currently under the INSULAIR® brand name.
In use, such a corrugated insulating liner has been found to provide superior insulating character through the presence of air space between the inner and outer layers of the blank. When filled with a hot liquid, such as coffee or tea, the air space substantially prevents the transfer of heat from the liquid to the hands of the consumer. The INSULAIR container has received wide acceptance in the marketplace due to its exemplary insulation characteristics.
While a corrugated liner provides suitable air space for superior insulation in the assembled INSULAIR container, it has been found that if the corrugations become spread or collapse, the insulating character of the container can be reduced. Such spreading or collapsing can generally occur during one or more of: a) storage of the blanks prior to conversion into a container; b) manufacture of the container; or c) during storage of the container by nesting or stacking a plurality of containers prior to use. When the blanks or finished containers are located at or near the bottom of a stack, the spread or collapse of the corrugated insulating layer can be quite acute due to the weight of the upper blanks or containers in the stack on the lower blanks or containers in the stack.
The decreased efficiency of insulation resulting from spread or collapse of the insulating liner is believed to be due to the decrease in the amount of effective air space between the inner and outer layers of the container. For example, the inventors have found that a liner having a corrugation thickness of about 0.040 inches upon manufacture of the liner can lose as much as 0.03 inches in corrugation thickness when the blanks are stacked for a few days prior to conversion into a container.
In typical corrugation applications, such as in the manufacture of boxes, the problem of corrugation spread or collapse is generally addressed by applying glue to the peaks (and/or valleys) of the corrugations prior to application of one or two outer sheets of paper to provide the corrugated material for use. The glue substantially prevents the flutes of the corrugated liner from spreading or collapsing. However, because the blank used to make the INSULAR multilayer container must be wound on a mandrel, it is not readily possible to use the gluing technique to reduce or prevent the spread or collapse of the insulating liner.
Moreover, while INSULAIR containers are presently the most prevalent multilayer container in the market, other multilayer containers having insulating layers have been proposed in, for example, U.S. patent application Ser. Nos. 11/283,772 and 11/182,330, the disclosures of which are incorporated herein in their entireties by this reference. Further examples of multi-layered corrugated container are set forth in U.S. Pat. Nos. 5,839,653 and 6,253,995, the disclosures of which are incorporated herein in their entireties by this reference. It is expected that any reduction in the integrity of the corrugation in such multi-layer containers would also decrease the effectiveness of insulation.
Accordingly, it would be desirable to develop a method to reduce the propensity of a corrugated insulating liner incorporated in a multi-layer container to spread or collapse in storage or use. Still farther, it would be desirable to obtain a corrugated liner for use in a multi-layer container, where that liner exhibits a reduced propensity to spread or collapse in storage or use.